This invention relates to electrical transmission of various information concerning a lens to a camera body and, more particularly, to a contact arrangement in an interchangeable lens camera for electrical transmission of specific diaphragm value (fully opened diaphragm value, fully closed diaphragm value), and switching information such as AUTO (automatic diaphragm control), and MANUAL (manual diaphragm control) of the lens to the camera body.
A photographic camera of automatic exposure control type has usually been operated in two modes. In the first mode, an exposure time (shutter speed) is set with priority at the operator's will so that the exposure time thus set is followed by the corresponding lens aperture for automatically obtaining a proper exposure (this mode is generally referred to as automatic exposure control of shutter priority type). In the second mode, a desired diaphragm value is preset at the operator's will and the corresponding exposure time is automatically controlled on the basis of said preset diaphragm value so that a shutter operation at said exposure time gives a proper exposure (this mode is generally referred to as automatically exposure control of diaphragm priority type).
For convenience of explanation, said former mode will be referred to simply as AUTO (automatic diaphragm control) and said latter mode will be referred to simply as MANUAL (automatic shutter control) in the following description. It should be realized that the term "MANUAL" is also used in a broader sense including also a case where photographing is carried out with the diaphragm and the shutter speed both being optionally determined at the operator's will.
With a photographic camera by which one of said both modes are selectively used to perform photographing by utilizing a single camera body and various lenses interchangeably mounted on this camera body, it is necessary to transmit information concerning the respective lenses such as the fully opened diaphragm value and the fully closed diaphragm value of the particular lens to the associated camera body, as already described in application Ser. No. 229,879, filed on Jan. 30, 1981, and applications Ser. No. 235,839 and Ser. No. 235,840, filed on Feb. 19, 1981, by Fumio Urano, Zenichi Okura, and Masahiro Kawasaki, corresponding to Japanese patent applications No. 1980-10978, No. 1980-19965, and No. 1980-19966, respectively. The disclosure of these applications is incorporated herein fully by reference.
For automatic exposure control and display of a shutter speed or a diaphragm value based thereon, the information concerning the respective interchangeable lenses such as the fully opened diaphragm value and the fully closed diaphragm value generally is mechanically transmitted to the camera body when the lens is mounted on the camera body. However, such mechanical solution has been disadvantageous in that the necessary high precision information transmission complicates and expands the bulk of the mechanism, increasing the price of the respective interchangeable lenses.
Said prior patent applications have proposed as a solution transmission of the information concerning the lens from the lens directly to the camera body in the form of electrical signals through electrical contacts arranged on mounts of the camera body and the lens, respectively, and biased to project from the associated mounts so that the circuit is closed simultaneously when the lens is mounted on the camera body. With such arrangement, however, there arise problems concerning the information transmission to the electrical contacts on the camera body for AUTO and MANUAL, respectively. For example, one such problem is reading the specific diaphragm values interrupted under intervention of the contact engagement for transmission of the information concerning the fully opened diaphragm value and the fully closed diaphragm value, the mount clamping screws and the lock groove. Furthermore, the power source tends to be prematurely consumed due to the circuit design. Display of control as well as arithmetic operation also creates problems.